Also referred to as the BTR-Complex: the feeling of emptiness after the end of a tv-series or movie, when

1) having to face the fact that all good things come to an end
2) having to let go of the bond that was built with the characters.

Leads in many cases to: addition to fan-fiction, discussion of every episode, and a re-watch of the tv-series/movie.

Durations range from an hour to multiple years.

Frank: "Hey buddy! What's up with Jimmy? He hasn't spoken a word today!"
Dennis: "I know. He just finished the last episode of Freaks and Geeks, and now he's having a Back-To-Reality complex..."
Frank: "Damn... How long do you think this will last?"
Dennis: "He'll get over it pretty soon for now, but after he does a re-watch of the series, it may last a little longer."